This project will provide valuable information on a population about whom little is currently known -- namely the severely mentally ill members of health maintenance organizations (HMOs). Specifically, we will identify HMO members with severe mental disorders and then we will prospectively study the services they receive in the HMO. The study will monitor the health services utilization patterns of 250 Kaiser Foundation Health Plan enrollees diagnosed as having schizophrenia or bipolar affective disorder. These individuals will be located by reviewing automated pharmacy records and tardive dyskinesia monitoring log books. The subjects' use of general medical and mental health services during the next two years of HMO membership will be recorded. Factors that predict termination from the HMO will also be studied. The severely mentally ill subjects' patterns of medical care utilization within the HMO will be compared with those of 250 matched control HMO members. Finally, the severely mentally ill subjects' retention within the HMO will be compared with that of the controls. These data will allow us to describe the treatment patterns and utilization experience of severely mentally ill persons in an HMO. Given the rapid increase in HMO membership, this information is urgently needed by policy makers and health care planners.